Northern Territory Police have a 38-year-old woman and a 46-year-old man in custody in relation to the incident, but charges have yet to be laid.

They say the incident started at a property in Virginia and continued to the Stuart Highway where witnesses saw two cars being driven on the wrong side of the road and up to a dozen shots fired.

One woman in her 60s is now in hospital in a serious but stable condition after receiving a gunshot wound to her arm while a man was treated at the scene for a wounded hand.

Commander Richard Bryson said the incident was related to a custody dispute, and the parties were known to each other.

"The (female) offender left the scene after incident then travelled to Humpty Doo and picked up a child that was known to offender from school," he said.

"Before (the female offender and child) were located, police had no vision over what that person's intention was in relation to that child."

Commander Bryson said 70 minutes elapsed between the time the incident was reported to when the offender was in custody, and Police worked to get traffic moving again as soon as it was safe.

"This is a very serious incident and we should be thankful no one else was injured. From a policing point of view, it's as serious as it gets."

The Stuart Highway near Howard Springs was closed for more than an hour yesterday to establish a crime scene.

A caller in the area told Vicki Kerrigan on 105.7 Drive he had heard two gun shots and saw "bits flying off a 4WD". One of the vehicles involved is believed to be held at Palmerston police station with a bullet hole in its window.

Traffic was backed up significantly through peak hour and began to move again after roads going south were reopened.